Yale University researchers have uncovered the molecular tricks used by bacteria to fight the effects of fluoride used in toothpaste and mouthwash to combat tooth decay. In the December 22, 2011, online issue of the journal Science, researchers report that sections of ribonucleic acid (RNA) messages called riboswitches—which control the expression of genes—detect the buildup of fluoride and activate the defenses of bacteria, including those that contribute to tooth decay. The senior author of the study states that these riboswitches are detectors made specifically to see fluoride. The riboswitches work to counteract fluoride's effect on bacteria; if the level of fluoride in the bacteria builds up to toxic levels, a fluoride riboswitch grabs the fluoride and then turns on genes that can overcome its effects. Since both fluoride and some RNA sensor molecules are negatively charged, they should not be able to bind, but they do. The researchers were stunned when they uncovered fluoride-sensing riboswitches. Although scientists would argue that RNA is the worst molecule to use as a sensor for fluoride, the researchers have found more than 2,000 of these strange RNAs in many organisms. By tracking fluoride riboswitches in numerous species, the research team concluded that these RNAs are ancient—meaning many organisms have had to overcome toxic levels of fluoride throughout their history. Now that these sensors and defense mechanisms are known, it may be possible to manipulate these mechanisms and make fluoride even more toxic to bacteria. Fluoride riboswitches and proteins common in bacteria are lacking in humans, so these fluoride defense systems could be targeted by drugs. (Source: ScienceDaily, December 22, 2011; reprinted from materials provided by Yale University)